Generally, engines used in Power, Marine and Industrial (P, M & I) application are continually subjected to stricter emissions levels. The engines in these applications typically include a piston and a cylinder liner developed to meet Tier-3 levels of emission standards. Wear of particular rings of a piston ring set can cause non-compliance with emission standards, oftentimes more quickly than desired.
For example, an increased wear rate of the piston ring set may be caused due to ring-to-piston groove side clearance under P, M & I operations (and even rail operations). The P, M & I operations are well known for their extreme service levels at relatively high engine outputs. Power assemblies, including piston compression rings and oil rings on the piston demonstrating sporadic high ring-to-piston groove, can be subjected to relatively high wear rates. Thus the piston compression rings and oil rings are frequently replaced prior to customer-expected life cycle. The frequent replacement of the piston compression rings and oil rings may lead to customer dissatisfaction. Likewise, such premature removal, can increase warranty costs, and when not detected or remedied in time, may result in significant, related subsequent engine damage and loss of engine availability, not to mention emissions standards non-compliance.
China Patent Publication Number 2,043,44,302 describes an engine piston assembly. The engine piston assembly is provided with a piston structure and a piston ring set matched with the piston structure. The piston structure, the piston ring set and the inner wall of an air cylinder together form a residual gap channel which is provided with at least one or more annular sudden expansion swelling cavities and has the function of multi-stage throttling swelling. When mixed gas in an engine is compressed and ignited for combustion and swells for doing work, the residual gap channel will generate flow resistance and an energy dissipation effect in an effort to prevent the high-pressure mixed gas and high-temperature high-pressure fuel gas from fleeing or leaking from a combustion chamber and an air cylinder of the engine to a crankcase, with only a small amount of hydrocarbon emissions escaping from the residual gap. The engine piston assembly is provided to reduce carbon deposits inside the cylinder of the engine and hydrocarbon emissions in tail gas emissions.